Magnetic memory device having a perfluro-polyether film coated on an inner surface of its housing for entrapping dust

ABSTRACT

Mechanical components including a magnetic head 3 and a magnetic disk medium 4 are contained in a housing 6 separating from outside atmosphere 5. A perfluoro-polyether film 9 is coated on the inner surface of said housing 6 and the upper surface of a base 2 provided with the housing 6. Floating dust in the housing 6 adheres on and is incorporated in said perfluoro-polyether film 9 so that dust is removed from the space in the housing 6 thereby the space in the housing 6 is maintained at a clean state free from dust. As a result, the head flotation is stabilized, abrasion of the medium and the head can be avoided and the occurrence of head-crush can be prevented.

This application is a continuation, of application Ser. No. 08/008,195,filed Jan. 25, 1993, now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a magnetic memory device, wherein informationis magnetically written into or read out from a magnetic recordingmedium such as a magnetic disk, magnetic drum, a magnetic tape and thelike through a magnetic head and the like.

2. Description of the Prior Art

In a magnetic memory device, information is magnetically written intoand read out from said magnetic recording medium through the magnetichead (hereinafter referred to as the head) during which a magnetic headslider (hereinafter referred to as the slider) is maintained to contactwith a magnetic recording medium (hereinafter referred to as the medium)or to be separated from the medium by a thin air gap. As this type ofthe magnetic memory device, a magnetic tape memory device, a magneticcard memory device, a flexible disk memory device and a hard disk memorydevice are commercially available.

In the flexible disk and the hard disk device of these magnetic memorydevices, the head will be separated from the medium by a thin air gapwhen the medium is rotating due to an air pressure generated by therotation of the medium. On the other hand, a spring is attached to thehead in order to push the head toward the medium. Consequently, the headis maintained at certain position balancing a floating force by the airpressure with a force of the spring pushing the head against the medium.In all these magnetic memory devices wherein information is written intoor read out from the medium through the head which is separated from themedium, it is necessary to maintain the slider close to the medium asmuch as possible in order to maximize the storage density. For thispurpose, in case of the hard disk memory device for example, the widthof air gap between the slider and the medium is maintained at 0.2 μm inminimum.

In case the air gap is so much thin as mentioned above, flotation of thehead will be disturbed by dust floating in the housing and becomeunstable thus causing problems that the head having unstable flotationand the medium contact each other which results in abrasion of the headand the medium. Also, head-crush will occur due to such contact of thehead with the medium.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide amagnetic memory device, wherein abrasion of the medium and the head bydust can be prevented and head-crush can be avoided.

The magnetic memory device according to the present invention comprisesa housing separating mechanical components including the magnetic mediumfrom outside atmosphere and a perfluoro-polyether film coated on a wholeor a part of the inner surface of the housing.

Perfluoro-polyether, hereinafter referred to as PFPE, which can be usedfor coating of the inner surface of the housing in the presentinvention, includes one of the following repeating units: --OCF₂ --,--OC₂ F₄ --, --OCF₂ CF(CF₃)--, and --OC₃ F₆ --. As example of suchPFPEs, materials expressed by the following formula can be listed:

(1) F₃ C(OCF₂)_(p) (OC₂ F₄)_(q) OCF₂ OCF₃

(2) F(CF(CF₃)CF₂ O)_(m) C₂ F₅

(3) F(C₃ F₆ O)_(r) C₂ F₅

(4) GCF₂ (OCF₂)_(p) (OC₂ F₄)_(q) OCF₂ G

(5) F(CF(CF₃)CF₂ O)_(m) CF₂ G

(6) F(C₃ F₆ O)_(r) C₂ F₄ G

(7) F(CF(CF₃)CF₂ O)_(m) CF₂ JCF₂ (OCF₂ (CF₃)CF)_(m) F

(8) F(C₃ F₆ O)_(r) C₂ F₄ JC₂ F₄ (OC₃ F₆)_(r) F

(9) {F(C₃ F₆ O)_(r) C₂ F₄ }₃ L

where, p, q or r is either 1 or other positive integer and m is either 3or greater integer. And, G is a functional group selected from the groupconsisting of --COOH, --CH₂ OH, --COOR (R is either hydrocarbon,fluoro-hydrocarbon or aromatic hydrocarbon ), --CONHC₆ H₃ (CH₃)NCO,--N═N--NH₂, --SO₃ H, --CSOH, --COSH and a functional group shown in thefollowing formula (1). ##STR1## J is either --SO₂ NHCO--, --SO₂ NHCH₂--, --CH₂ N(OH)CH₂ --, --CONHCO--, --CONHCH₂ -- or --CSNH--. L is --CH₂(N(NH)--)CH₂ --.

According to the magnetic memory device of the present invention,because any dust in the housing adheres on PFPE film, the atmosphere inthe housing can be maintained at a clean state free from any appreciableamount of dust. The magnetic memory device according to the presentinvention thereby can stabilize the floating of the head and reduce theoccurrence of head-crush compared to the conventional magnetic memorydevice, and, in effect, the reliability of the device is significantlyincreased.

Although it is not exactly known what mechanism involves in trapping ofdust floating in the housing by PFPEs, but it is speculated that dustwill be buried and trapped in the PFPE film, because PFPEs are of softmaterials (most of PFPEs are liquid). The PFPE film is effective intrapping dust if the PFPE film is provided on the inner surface whereverin the housing.

However, the maximum trapping effect can be obtained if the region ofthe inner side walls of the housing which faces to the peripheralsurface of the magnetic disk medium or is located near the magnetic diskmedium are coated with the PFPE film. Such effect might be attained dueto a centrifugal force generated by rotation of the magnetic diskmedium. That is, dust particles floating near by the magnetic diskmedium are given a high impact energy by the centrifugal force therebybury in said PFPE film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a magnetic memory device according tothe first embodiment of the present invention:

FIG. 2 is a sectional view showing a magnetic memory device according tothe second embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, a first embodiment of the present invention will be described. Asshown in FIG. 1, a magnetic memory device 1 is provided with a rotaryspindle 10 on a base 2 and this rotary spindle 10 is connected to adriving shaft of a motor (not shown in the drawing) provided in the base2. A magnetic disk medium 4, facing its recording surface downwards, isattached to the rotary spindle 10 at its central part. By this rotaryspindle 10, the magnetic disk medium 4 is rotated with keeping itsrecording surface horizontally. On the other hand, a magnetic head 3 isplaced in contact with the lower recording surface of the magnetic diskmedium 4 and supported by a supporting member 3a made of flexiblematerial. The magnetic head 3 is arranged to be pushed on the lowerrecording surface of the magnetic disk medium 4 at a desired force bythe supporting member 3a. In order to separate a whole mechanical memberincluding these magnetic head 3 and magnetic disk medium 4 from theoutside atmosphere 5, a housing 6 is air-tightly provided on the base 2.That is, the housing 6 is provided on the base 2 in such a way to covera whole mechanical member including the magnetic head 3 and the magneticdisk medium 4.

And, on the inner surface 7 of the housing 6 (the inner wall of theceiling and the inner side walls 8) and the upper surface of the base 2,a PFPE film 9 is coated thereby a whole inner surface of the housing 6surrounding said mechanical members, i.e., a whole inner surface ofwalls defining a space in which said mechanical members are placed, iscoated with the PFPE film 9. This PFPE film 9 is comprised of F(C₃ F₆O)₂₀ C₂ F₄ CH₂ OH or GCF₂ (OCF₂)₁₃ (OC₂ F₄) ₈ OCF₂ G (where, G is afunctional group shown in said formula (1)). This PFPE film 9 can becoated on the inner surface by sweeping with a piece of cloth containingPFPE liquid.

In the magnetic memory device thus constituted, dust already existing inthe housing 6 before assembling of the magnetic memory device or dustcame into the housing 6 after assembling will float in the space betweenthe magnetic head 3 and the magnetic disk medium 4, but when floatingdust particles run into the inner surface 7 of the housing 6 and theinner upper surface of the base 2, they are trapped in the PFPE film 9coated on the surface thereby dust is removed from the inside of thehousing 6 where is kept free from dust. Therefore, unstable flotation ofthe head 3 due to dust can be avoided and also the occurrence ofhead-crush can be prevented.

FIG. 2 is a sectional view showing a magnetic memory device according tothe second embodiment of the present invention. In this embodiment, thePFPE film 9 is formed only on a part of the side wall 8 facing to theedge of the magnetic disk medium 4 in the housing 6. Floating dustparticles in the housing 6 run outward in the direction of the diameterof magnetic disk medium 4 by a centrifugal force or on the air flowgenerated by the rotation of the magnetic disk medium 4 thereby dustparticles come flying to a part of the inner side walls 8 near by themagnetic disk medium 4 in the housing 6 and adhere to the PFPE film 9provided on this part. Although there exist some dust particles comeflying to other parts, most dust particles fly outward in the directionof the diameter of magnetic disk medium 4. Therefore, in this embodimentthe cleaning in the housing 6 can be achieved, thereby unstableflotation of the head and head-crush can be prevented similarly as thefirst embodiment.

Next, the effect of embodiment of the present invention will beexplained, comparing with the conventional device. A magnetic memorydevice coated with a PFPE film 9 on a whole inner surface of a housing 6as shown in FIG. 1, hereinafter referred to as the device A, a magneticmemory device coated with a PFPE film 9 on a whole inner surface of ahousing 6 except for the area of side walls 8 near by a magnetic disk 4,hereinafter referred to as the device B, and a magnetic memory devicecoated with a PFPE film 9 on only a part of side walls of a housing 6near by a magnetic disk 4 as shown in FIG. 2, hereinafter referred to asthe device C were prepared. For the purpose of comparison, a magneticmemory device without coating with a PFPE film, hereinafter referred toas the device D, was also prepared. At least the surface of the housing6 facing to the inner space defined by the housing was formed withaluminum alloy. Also, all magnetic memory devices A, B, C and D, 30pieces each, were assembled in atmosphere containing dust particles ofdiameter not less than 0.1 μm at the rate of 10⁶ particles per 1 m³.

After 1000 hours operation, two out of 30 devices showed head-crush inthe device B. In the device D assembled for comparison, twelve out of 30devices showed head-crush. On the other hand, no head-crush could beseen in the devices A and C. As explained above, dust in the housing canbe removed by the PFPE film and the atmosphere in the housing can bekept in a clean state free from dust in the magnetic memory deviceaccording to the present invention, resulting in head-crush beingprevented.

What is claimed is:
 1. A magnetic memory device comprising:a housingmeans separating mechanical components means, including a magneticmedium means, from outside atmosphere, and coating means comprising aprefluoro-polyether film coated on whole or a part of the inner surfaceof said housing means for trapping dust which may be contained withinsaid housing means.
 2. The magnetic memory device according to claim 1,wherein said magnetic medium means is a circular magnetic disk mediumand said coating means comprising said perfluoro-polyether film iscoated on a part of the inner surface of said housing means and islocated at a position inside said housing means near a circumferentialperiphery of said magnetic disk medium.
 3. The magnetic memory deviceaccording to claim 1, wherein said magnetic medium means is a hard diskmeans.
 4. The magnetic memory device according to claim 1, wherein saidmagnetic medium means is a floppy disk means.
 5. A magnetic disk drivecomprising a closed housing means having a rotatable disk means therein,a slider means supported adjacent to and separated from said rotatabledisk means by an air gap, a film means on an inside wall of said housingmeans at least adjacent a circumference of said disk means forcollecting dust within said housing means, said film means being aperfluoro-polyetherfilm which collects said dust within said housingmeans.
 6. The magnetic memory device according to either claim 1 orclaim 5, wherein said perfluoro-polyether film contains one of therepeating unit taken from a group consisting of: --OCF₂ --, --OC₂ F₄ --,--OCF₂ CF(CF₃)--, and --OC₃ F₆.
 7. The magnetic memory device accordingto either claim 1 or claim 5, wherein said perfluoro-polyether film ismade of a material selected from the group consisting of:F₃ C(OCF₂)_(p)(OC₂ F₄)_(q) OCF₂ OCF₃, F(CF(CF₃)CF₂ O)_(m) C₂ F₅, F(C₃ F₆ O)_(r) C₂ F₅,GCF₂ (OCF₂)_(p) (OC₂ F₄)_(q) OCF₂ G, F(CF(CF₃)CF₂ O)_(m) CF₂ G, F(C₃ F₆O)_(r) C₂ F₄ G, F(CF(CF₃)CF₂ O)_(m) CF₂ JCF₂ (OCF₂ (CF₃)CF)_(m) F, F(C₃F₆ O)_(r) C₂ F₄ JC₂ F₄ (OC₃ F₆)_(r) F, and {F(C₃ F₆ O)_(r) C₂ F₄ }₃L,where, p, q or r is either 1 or other positive integer; m is either 3or greater integer; G is a functional group selected from the group of--COOH, --CH₂ OH, --COOR (R is either hydrocarbon, fluoro-hydrocarbon oraromatic hydrocarbon), --CONHC₆ H₃ (CH₃)NCO, --N═N--NH₂, --SO₃ H,--CSOH, --COSH and ##STR2## J is a functional group selected from thegroup of --SO₂ NHCO--, --SO₂ NHCH₂ --, --CH₂ N(OH)CH₂ --, --CONHCO--,--CONHCH₂ -- and --CSNH--; L is --CH₂ (N(NH)--)CH₂ --.
 8. The drive ofclaim 5 wherein substantially the entire inside wall of said housingmeans is covered with said film means.